Journal of Dental Research, Vol 75, 752-760, Copyright © 1996 by International & American Associations for Dental Research Online Journals
Analysis of edge-losses in reflectance measurements of pigmented maxillofacial elastomer
W. M. Johnston, N. S. Hesse, B. K. Davis and R. R. Seghi
Section of Restorative and Prosthetic Dentistry, College of Dentistry, Ohio State University, Columbus 43210-1241, USA.
Edge-losses occur during reflectance measurements of pigmented
maxillofacial elastomer when light is scattered within a sample beyond that
part of the surface exposed to the observation system of the optical
device. A custom sample-holder is presented which redirects light that
would not be measured during conventional reflectance measurement back into
the sample. The amount of edge-loss occurring within thin layers of
maxillofacial elastomer with tan pigment on black-and-white backings was
found to depend on sample thickness, the backing, the beam size used during
conventional reflectance measurement, and the optical term bS = (2KS +
K2)1/2. Data analysis revealed a significant interaction among these four
factors. Additionally, the edge-loss occurring during the tristimulus
reflectance measurement of thick samples of maxillofacial elastomer with
various concentrations of tan and black pigment was found to be linearly
related to bS up to a limiting value, with no additional edge-loss
occurring for bS values above this limiting value. Edge-loss is an
important consideration during the matching of the optical characteristics
of pigmented maxillofacial material to those of human skin.
